What techniques are used to begin creating new models?
There really are only ~6 in blender, except for impracticable ones/not supported, the rest are derivatives:
1. Mesh modeling:
This is where you use edit mode, and move around, connect and disconnect vertices to form a shape.
There are a lot of sub-approaches, like extrude modeling and box modeling to name a few. As a rule, use extrude modeling if you're not going to have to eyeball proportions, since you can use the details from the start and work faster (like modeling off blueprints), and use box modeling for when your eyeballing stuff since it is much easier to adjust proportions.
Some people only like to do it one way, I'd try both and see what you like.
In this area Blender has very good tools.
2. Sculpting:
This is where you work off of a very high poly mesh, and form a shape by pushing vertices in large numbers to form a shape, this can produce very creatve and organic workflow, generally used form non hard surface meshes, although some people sculpt hard surface meshes.
In this area, Blender has quite good tools.
3. Curve modeling
This is where a form is created using joined curves, spline modeling. This technique has been largely fased out, but was popular in the 90's (I think)
The most famous form is NURBS modeling, where you can create surfaces between curves, but as I said few people now use that method.
Blender does have curve support, but no support for trimming or viewport UV's.
4. Procedural Modeling:
This is where code/modifiers does the modeling work. A good example is the displacement modifier, where a mesh can be distorted based on a height map. It is easy to create rock surfaces using this technique.
With code added, procedural modeling can go very very far, see these videos. https://www.youtube.com/watch?v=jOLhnwllpgs &amp; https://www.youtube.com/watch?v=WP473rNZ_Eo
Blender's tool set here aren't so advanced, though there are external add-ons that can help: eg: https://github.com/nortikin/sverchok
5. Simulation
This is useful only for things like a fluid, liquid or gas/ it also is useful for modeling damage or clothing.
The fluid and to some degree the smoke simulator are limited, but the  cloth simulator is pretty well featured
6. Metaballs
These are basically shapes that are enclosed in what can best be descried as a shrink wrap shell... They merge together, making it easy to modeling something like a peanut. When they are separated sufficiency they split and go back to their original form. There are few practical applications I know of for meta balls in blender.
See: http://en.wikipedia.org/wiki/Metaballs (this example only shows a few but you can have 100's)
Other Methods of Modeling:
These mostly include scanning and photo-modeling, but Blender doesn't include tools to do this out of the box, you'd need specialized software for this.